The successful production of neural prostheses, especially those for use in cortical areas, requires the use of very thin and highly efficient biocompatible fiber electrodes which cancontinue to work reliably during longterm residence in the body. Improved performance of these electrodes is expected if they can be coated with a highly adherent layer of iridium oxide. Such a coating is biocompatible and will not dissolve under applied potentials. This program is aimed at investigating whether a combination of reactive rf deposition and ion beam attachment methods can be used to create such a coating. The program involves deposition under a matrix of conditions, electrochemical testing and examinations of adhesion and structural integrity. The use of ion beam integration techniques will allow highly adherent electrode coatings to be deposited on nearly any substrate, including metals, ceramics and polymers. This will permit he fiber material to be chosen for its mechanical and electrical properties without regard to its surface activity, and its surface tailored to meet the needs of sufficient current injection at low voltage.